Wireless telecommunications networks are built to accommodate mobile telephones and personal communication systems (collectively, mobile telephones and PCSs are referred to as "mobile stations") that are typically low powered. The mobility and low power requirements of these mobile stations impose major design constraints, not only upon these devices themselves, but upon BSS units and wireless telephony switching offices, commonly referred to as Mobile Switching Centers ("MSCs"), that provide communication means between the mobile unit and some other wired/wireless station.
Turning momentarily to FIG. 1, illustrated is a block diagram of a prior art infrastructure (generally designated 10) that includes a plurality of mobile stations 105, a plurality of Base Transceiver Stations ("BTSs") 110, a BSS 115, a speech transcoder unit ("STU") 120, a plurality of MSCs 125 and a Public Switched Telephone Network ("PSTN") 130, all of which are directly or indirectly linked together to form infrastructure 10.
BSS 115 is associated with multiple BTSs 110 (e.g., transceiver sites or cells) and STU 120 for communication between mobile stations 105 and a given MSC 125. Generally speaking, many BTSs 110 are built within a defined geographic area, so that BTS density causes each mobile station to be "close" to at least one BTS 110 at all times.
Wireless communication systems employ multiple BTSs 110 linked to a central computer associated with MSC 125 for coordination. BTSs 110 also overlap one another and typically operate at different transmitting and receiving frequencies to eliminate interference. Conventionally, wireless communication systems (e.g., Frequency Division Multiple Access ("FDMA"), Time Division Multiple Access ("TDMA"), etc.) commonly separate multiple wireless transmissions over a finite frequency range, allocating a discrete amount of frequency bandwidth to each mobile station to permit many concurrent conversations.
Each mobile station 105 is usually assigned a specific time slice/slot for transmission, occupying a finite amount of available frequency spectrum--the wireless telephony frequency band consists of several hundred channels/frequency slots available for conversations.
Within each BTS 110, approximately several dozen channels are available for mobile stations 105, different channels are therefore allocated for neighboring cell sites, allowing for re-use of frequencies with only minor amounts of interference. When a mobile station 105 is activated, it hunts (or searches) available communication channels for the strongest signal and locks onto it (note, if signal strength fades while in motion, mobile station 105 automatically switches (a "handoff") signal frequencies or BTSs 110, as necessary).
With reference to FIG. 1, BSS 115 includes a 64K time slot interchanger ("TSI") 160 and a plurality of subrate switching equipment modules 165. In addition, a select channel for communication with BTS 110 is one of wireless communication channels 140. Conventionally, the selected wireless channel 140 communicates an incoming call from mobile station 105 to BTS 110, BTS 110 in turn communicates the same to BSS 115 over one of communications trunks 145, BSS 115 communicates the same to STU 120 over one of communications trunks 150, and STU 120 in turn communicates the same to MSC 125 over one of communications trunks 155. The incoming channel on communications trunk 145 (channel A of channels A-D in this example) is chosen by BTS 110 and the outgoing channel on communications trunk 150 (channel E of channels E-H in this example) is chosen by MSC 125. This results in connection A-E through ESS 115 via module 165A.
Assume now that a second incoming call from the same BTS 110, and in the same BTS timeslot as the prior incoming call, must be connected through BSS 115 to STU 120. As MSC 125 is conventionally responsible for selecting one of communications trunks 150 (and hence STU 120 communications channel), it is very unlikely that an optimal connection in relation to existing connections (A-E) through BSS 110 may be made. Most often random connections will be made, resulting in connection such as B-J through BSS 115 via modules 165A, 165C.
If intelligent means existed to select a connection through BSS 115 to STU 120, an optimal selection would have been through channel F, allowing reuse of connection A-E to thereby conserve communications system resources (e.g., connection B-F) and subrate switching resources (e.g., module 165C). Commonly, the trunks for mobile station originated calls are hunted by MSC 125, this in point of fact a standard procedure of the GSM wireless standard. Such procedures, however, do not encourage an efficient use of BSS 115 and MSC 125 resources. There consequently exists a need in the art for improved systems and methods that allow BSS 115 to hunt for trunks used by call originated by mobile station 105 to increase MSC 125 call capacity and decrease waste of BSS 115 communications resources.